In production of tubular metal articles by centrifugal casting in a metal mold which has an inner or active surface which is circular in cross section transverse to the axis of mold rotation, it is desirable to apply to the active surface of the mold a layer or layers of particulate material, with the layer ranging from a relatively narrow ring, as in the case of an end ring or an internal ring, to a layer completely covering the mold surface. In the case of an end ring, the ring simply serves to retain the molten metal being cast within the mold. In the case of an internal ring, the ring may serve as a portion of the surface against which the metal is to be cast, or may act to separate two castings made simultaneously in the mold. A layer covering the entire active surface of the mold constitutes the surface against which the molten metal is cast. In many prior-art practices, end rings for centrifugal casting molds have been in the form of preformed hardened refractory cores backed up by metal rings, and internal rings have been in the form of preformed refractory cores only. Layers covering the entire active surface of the mold have usually been of refractory material applied in various fashions.
While such rings and layers of various types are commonly employed in the centrifugal casting industry, there has been a need for a simple method for establishing such layers from particulate material, and for a simple and inexpensive apparatus for accomplishing such a method.